1. Field of the Invention
The present invention relates to a coil transformer composed of a unit configuration. More specifically, the present invention provides a plurality of (n number of) coil units, wherein external coupling terminals of the coil units are mutually connected to configure a transformer having a desired capacity.
2. Description of the Related Art
Conventionally, companies were able to perform energy administration per factory or per business office. However, due to the revision of the Rationalization in Japanese Energy Use Law, companies using a total energy of 1500 kl or higher in a year as a whole entity are now required to report to the government the amount of used energy and be designated as specified entities. In addition, by the enforcement of the transformer characteristics improvement act (adopting of top runner transformers) in 2006, it is now necessary to reduce the loss generated from the coils (hereinafter referred to as load loss).
The load loss in coils is broadly classified into a resistance loss generated by current flowing through the resistance of the winding wires and an eddy current loss (stray loss) generated by the leak magnetic flux from the iron core being interlinked with the winding wires. There are many types of winding wires, but the most dominant type in realizing a large-capacity device is an edgewise winding wire which is strong against electromagnetic mechanical force during short-circuit. However, since the edgewise winding wire has a large area interlinked with the magnetic flux, stray loss is increased. Therefore, along with the increase of load loss and rising of winding wire temperature, the cross-sectional area of the wire must be increased, according to which the transformer size is increased and the material costs are increased by the escalating material prices.
As described, edgewise winding wire transformers have been known. Patent document 1 (Japanese patent application laid-open publication No. 2005-158857) discloses a resin mold coil comprising a coil formed by winding a conductor and an insulation layer which is formed on the inner and outer peripheries of the coil, wherein the coil is formed by stacking, in the axial direction, a coil having an element wire wound several times from the outer to the inner periphery in the radial direction and a coil having the element wire wound several times from the inner to the outer periphery, for example, the direction 3 as shown in FIG. 1, and wherein the circumference of the coil is coated with the resin to obtain insulation. Thus, a mold coil having superior heat dissipation property, insulation property and workability during manufacturing is provided, which is down-sized and strong against electromagnetic mechanical force during short-circuit.
Furthermore, patent document 2 (Japanese patent application laid-open publication No. 9-186028) discloses a transformer provided with a switch for switching the connection of two windings in series or in parallel, wherein a high-voltage winding which is a series-parallel changeover winding in which the winding ratio is approximately 2:1 is provided as a primary winding or a secondary winding, and wherein a tapped winding is arranged outside the high-voltage winding. According to the disclosed art, the outer diameter dimension of the whole body of the winding can be downsized since there is no need to provide a space for forming an opening for drawing out the tap winding.
Moreover, patent document 3 (Japanese patent application laid-open publication No. 7-220955) discloses a non-voltage tap switching device wherein switching between parallel and series connection of a transformer winding divided into three parts can be readily performed inside a transformer. According to the disclosed art, movable contacts are rotated by operating a driving shaft which is drawn out of a transformer tank, and the connection between fixed contacts is switched, so as to switch the transformer windings divided into three between series and parallel connection.